I’m not really great at fantasy football but I’m in a long running league of beer buddies. In order of where points come from and usual draft order:
Running backs (typical 2 must play)
Quarterbacks (1 must play)
Receivers (typical 2 must play)
Flex (additional RB or receiver) (1 play)
Tight End (1 play)
Kicker (1 play)
Defence (the leagues I play have entire defense as a pick) (1 play)
Your bench will have a few slots as well.
Things to pay attention to are the stats like PPG (points per game) from prior season, projected points THIS season, and specific things like touchdowns, etc. You also want to keep an eye on the bye week listed for each player. You don’t want half your good guys having the same bye week, your team will not do well if so.
Week to week you can check the waivers for released players, drop players that go on Injured Reserve, etc. The services will recommend who you should play, it’s really easy.
Most leagues have dead teams where someone just never signs in. Most people who play don’t have time to check everything every week. It’s mostly enjoyable banter and commentary and an extra reason to pay attention to scores by teams you don’t normally follow.